This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Subcellular localization and translation of mRNAs provides cells with a locally renewable source of proteins to autonomously respond to extracellular stimuli. For neurons, this is critical since the cytoplasm and membranes of neurons can extend for several hundred times the dimensions of the cell body. Work in developing neurons has shown that localized protein synthesis plays a role in axonal pathfinding, provides structural protection to the axon, and triggers anterograde and retrograde axonal transport. Studies from the PI's group have shown that axonal protein synthesis is triggered by injury in adult neurons and that regenerating axons show particularly robust intra-axonal protein synthesis. This localized protein synthesis represents a mechanism that could be modulated to facilitate the regenerative capacity of axons in the adult nervous system. Despite the obvious functional significance of and newly increased interests in axonal protein synthesis, we know of excessively few mRNAs whose local translation is regulated by extracellular stimuli. Our preliminary studies indicate that adult axons have the potential to synthesize a complex population of more than 200 different proteins. We hypothesize that axonal stimulation alters localized protein synthesis through both directing the transport of particular mRNAs into the axonal compartment and locally controlling the activity of the axonal translational machinery. The objective of this BioAMS project is to use the high sensitivity of AMS for quantifying how protein synthesis is regulated in regenerating axons.